Review Question - QID 212901

An isotonic muscle contraction is a muscle contraction with constant tension such as the upwards and downwards motions of a biceps curl.

The word “isotonic” is derived from two Greek words: “iso”, meaning “same”, and “tonikos” meaning “tension”. An isotonic muscle contraction is one during which the muscle maintains the same tension as it shortens. There are two types of isotonic contractions: concentric and eccentric. In a concentric isotonic contraction, the muscle shortens while contracting. In an eccentric isotonic contraction, the muscle lengthens during contraction.

Ashe et al. review exercise programs used in physical therapy. They report that muscle strengthening can be classified into isotonic, isometric, and isokinetic contractions. Isotonic exercises involve the development of muscular force through range of motion or movement. Isokinetic exercises involve the force generation at a constant speed. Isometric exercises involve the development of force without movement, as in tensing and holding a muscle at a certain part of the range.

Illustration A is an image which illustrates the difference between isotonic and isometric contractions.

Incorrect Answers:
Answers 1 & 2: The upwards and downwards motion of a biceps curl are both examples of isotonic muscle contractions
Answers 3 & 5: Pushing against a wall is an example of an isometric muscle contraction.